The present invention relates to a bearing apparatus, and more particularly, to the bearing apparatus in which an outer ring is supported by an axle box so as to move in an axial direction.
Conventionally, as a bearing apparatus to be used in a motor, for example, there has been known a bearing apparatus including a pair of rolling bearings, one of which is positioned at a fixed side and the other is positioned at a free side, and so constructed that an outer ring of the rolling bearing at the free side is fixed to an axle box provided with a key groove in a manner restrained from rotation by means of a key member, and supported so as to move in an axial direction, thereby to absorb a difference in thermal expansion of a rotation shaft during operation (JP-A-2004-239388). In JP-A-2004-239388, it is disclosed that a key hole in a columnar shape or in a square pillar shape is provided on an outer peripheral surface of the outer ring of the bearing, and a lower end of a key member in a columnar shape or in a square pillar shape is inserted into the key hole, while an upper part of the key member is movably inserted into the key groove in the axle box, thereby permitting the outer ring and the axle box to move within a range of the key groove.
Although ceramics are preferably employed as material for the rolling bearing which is used in an environment where thermal expansion must be taken into consideration, it is difficult to work the keyhole in a columnar shape or in a square pillar shape in brittle material such as ceramics. Therefore, there is a problem that the bearing apparatus disclosed in JP-A-2004-239388 can be applied only in case where metallic material such as bearing steel is employed as the material for the bearing, but cannot be applied in case where the brittle material is employed.